1. Field of the Invention
The present invention is generally concerned with the reliability of information transmission links and more particularly a device for assessing the transmission quality of a transmission optical amplifier equipment used on an optical transmission link, such assessment being carried out, among other things, to enable activation of a mechanism for re-establishing the transmission quality of the link in the event of deterioration of the transmission quality of the amplifier equipment.
The amplifier equipments may be intermediate amplifier equipments or repeaters disposed at regular intervals along a link and amplifying the signals conveying said information in order to compensate the attenuation resulting from their transmission on the link.
2. Description of the Prior Art
In the case of optical links and in the more particular case of transmission of digital information on an optical link intermediate equipments called regenerators are used to process the signals obtained after optical-to-electrical conversion of the transmission signals transmitted on the link, the regenerator equipments not only amplifying the resulting electrical signals but also reconstituting them as faithfully as possible, given the digital nature of the information.
A known method for assessing the transmission quality of regenerator equipments is to include a parity binary digit in the code used to transmit the information and to measure the error rate affecting said electrical signals in the regenerator equipment.
Since the invention of optical amplifiers such as doped fiber optical amplifiers and semiconductor optical amplifiers, for example, which are able to amplify optical signals directly, it has been possible to use these amplifiers as intermediate amplifier equipments on an optical link. These amplifiers can also be used as amplifier equipments at the ends of a link, to obtain a sufficient transmit and/or receive level.